Is there a maximum limit on the number of hashMap key vals in motoko?

haida · October 1, 2022, 2:36pm

Is there a maximum limit on the number of hashMap key vals in motoko? Will excessive hashMaps (such as 1 billion records) affect the write and read speed?

h1teshtr1path1 · October 1, 2022, 3:17pm

github.com

dfinity/motoko-base/blob/master/src/HashMap.mo

/// Mutable hash map (aka Hashtable)
///
/// This module defines an imperative hash map (hash table), with a general key and value type.
///
/// It has a minimal object-oriented interface: `get`, `set`, `delete`, `count` and `entries`.
///
/// The class is parameterized by the key's equality and hash functions,
/// and an initial capacity.  However, as with the `Buffer` class, no array allocation
/// happens until the first `set`.
///
/// Internally, table growth policy is very simple, for now:
///  Double the current capacity when the expected bucket list size grows beyond a certain constant.

import Prim "mo:⛔";
import P "Prelude";
import A "Array";
import Hash "Hash";
import Iter "Iter";
import AssocList "AssocList";
import Nat32 "Nat32";

This file has been truncated. show original

May be this will help. You can look into the implementation, how read/write is done, and parent structure of Hashmaps for performance.

rossberg · October 1, 2022, 3:47pm

There is no artificial limit other than memory size. But the 4 GiB of Wasm memory will run out long before you can reach 1 billion entries. Depending on what you store, I would expect less than 100 M entries in practice, even in the ideal case (i.e., when merely mapping Int to Int).

For a scalable solution, you need to be able to distribute your data over a dynamic number of storage canisters.

Topic		Replies	Views
Champ Map for Motoko - A Faster/Cheaper/Scalable Map Showcase	4	187	April 27, 2026
HashMap Inputs/Meanings Language Support Motoko	6	1618	June 3, 2020
Efficient data structure for a large data Developers Functional-Programming	4	104	December 31, 2024
Two questions about canister storage Developers	30	3726	March 9, 2022
Typical instruction limits Developers	2	503	October 7, 2022

Is there a maximum limit on the number of hashMap key vals in motoko?

Related topics